Patients who undergo medical treatment in hospitals frequently require both extraction of blood for blood testing purposes and intravenous administration of medical fluids. Proper treatment of the patient may require that the blood be extracted and the medical fluids administered repeatedly and on a regular basis. In the past, this procedure has required that multiple needle insertions be made in various locations of the patient's body to access veins such as the external or internal jugular, subclavian, cephalic, femoral or saphenous veins. Multiple needle insertions not only result in considerable discomfort to the patient but also increase the risk of infection and compound the danger that medical personnel will be pricked by a contaminated needle.
Conventional methods of drawing blood from a patient typically utilize partial vacuum pressure to draw the blood from one of the patient's veins into a collecting device. Such utilization of partial vacuum pressure to draw blood from the vein tends to prematurely collapse the vein, thus necessitating re-insertion of the collecting device in another vein or in the same vein at a separate location to draw additional blood. This problem is particularly common in the drawing of blood from infants and the aged, in which small, thin veins are typically the source for blood samples. Accordingly, a device is needed which facilitates both collection of blood from and administration of medical fluids to a patient on a repeated basis using one, rather than multiple, needle insertions and which prevents premature collapse of a vein by utilizing intrinsic venous blood pressure to collect blood.